STEP-BY-STEP INSTRUCTION FOR EXAMPLE 9

This image sample group consists of 10 pairs of synthetic PIV recordings and a calibration grid image of 11 vertical and 11 horizontal lines, which are simulated for a four-roll-mill flow PIV test. The axis of the camera is not set vertically to the measurement plane, so that the images are distorted. The simulated physical area is 100-mm X 100-mm. The angle between the camera axis and measurement plane is 30 degree. The followed 4-part instruction demonstrates: how to create a calibration function (Part 1); how to calibrate a group of distorted PIV images (Part 2); how to evaluate the calibrated PIV images (Part 3); and how to evaluate a group of distorted PIV images with interrogation grid transformation, i.e. without image calibration, (Part 4).

PART 1 - CREATE IMAGE CALIBRATION FUNCTION

Step 1: Import calibration grid

- Execute file “Edpiv.exe” - The start window is shown on the screen;

- Click menu “File \ Open recording 1” to load image “…\ PIVsamples \ 9_DistortedImages\ Data \ CalibrationGrid.bmp”.

Step 2: Determine grid marker positions

- Press button “Evaluation” to open “Evaluation window”;

- Press button Gto hide evaluation grid lines;

- Press button Pto hide evaluation points;

- Increase window size to clearly see details of the target grid lines (i.e. 11 vertical & 11 horizontal lines);  

- Select menu “Tools \ Calibration markers \ Individual search ”;

- Move the mouse arrow to include the intersection of the 2nd vertical and 2nd horizontal (from bottom and left) calibration grid lines in the square frame, and the press left mouse button - dialogue box “Image pattern for calibration marker search” appears;

- Set parameters as
IPT settings:
Synthetic image pattern
W width [pix]:
32
S radius [pix]: 12
Shape: button “+” pushed down
Intensity: 
button “P” pushed down
Size variation [%]:
H=0, V=0.5, O=0.5
and then click menu “Match angles”;

- Press “OK” button - dialogue box “Add/edit calibration makers” appears;

- Input parameters as
X-obj [mm]:
10
Y-obj [mm]:
10
and then close dialogue box “Add/edit calibration makers”;

- Find other three grid markers in the same way so that:
Intersection of 10th vertical and 2nd horizontal lines for (90,10)
Intersection of 2nd vertical and 10th horizontal lines for (
10,90)
Intersection of 10th vertical and 10th horizontal lines for (
90,90)
More points may be added to make the calibration more reliable;

- Press “TJ” button to disable the individual marker search function.

Step 3: Create and test calibration function

- Select menu “Tools \ Calibration function \ Create function” - Dialogue box “PIV cameras” appears;

- Select “Normal” and press button “OK”;

- Press “OK” to close the information box with message “The calibration function is ready!”

- Select menu “Tools \ Calibration function \ Image effect” - Dialogue box “Distorted image calibration” appears;

- Set up parameters as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100;
Calibrated image frame:
same
Stereo camera:
N;

- Press button “OK” to close the dialogue box - An calibrated grid image displayed in the window;

- Close “Evaluation” window.

Step 4: Export calibration function

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Click mouse at calibration function check button “N” - Dialogue box “Calibration function” appears;

- Select radio button “Export” and then press button “OK” - Dialogue box “Export image calibration data” appears;

- Find a destination folder, input a file name and press “save” button;

- Close EDPIV.

 

(a) Grid image before calibration

 

(b) Grid image after calibration

 

 

PART 2 - CALIBRATE A GROUP OF IMAGES

Step 1: Generate image file list

- Execute file “Edpiv.exe” - The start window is shown on the screen;

- Select menu “Edit \ File list” - Dialogue box “Creating file list” appears;

- Press “Input files” button - Dialogue box “Data file list” appears;

- Browse hard drives to find folder “…\ PIVsamples \ 9_DistortedImages\ ”;

- Arbitrarily select one of the Windows Bitmap (BMP) files, and then press “Open” button;

- Press “Output file” button - Dialogue box “Data file list” appears again;

- Browse the hard drives to find an empty folder (or create a new folder);

- Type a name for the file list in the edit box indicated by “File name”, and then click “Save” button;

- Set “Recording type” to 2;

- Press button “Create” to generate the image file list;

- Close the dialogue box to return to the start window.

Step 2: Open PIV image group

- Click menu “File \ Image group” in the start window - Dialogue box “Recording group” appears;

- Browse the file system to find the image file list created in step 1;

- Click “Open” - The first image of the first pair is shown in the picture frame.

Step 3: Import calibration function

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Click mouse at calibration function check button “N” - Dialogue box “Calibration function” appears;

- Select radio button “Import” and then press button “OK” - Dialogue box “Import image calibration data” appears;

- Browse hard file system to find the file created in Part 1, Step 4, and press “Open” button;

- Close dialogue box “Stereo/distorted PIV recording”.

Step 4: Calibrate image group

- Press button “Processing” to open “Image processing” window;

- Click menu “Edit \ Image group \ Calibration” - Dialogue box “Settings for image group processing” appears;

- Select start and end number of the images (e.g. 1and 20), determine the file names for the processed images (e.g. “Original”), and press “OK”;

- Setup parameters in dialogue box “Distorted image calibration” as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100;
Calibrated image frame:
same
Stereo camera:
N;

- Press “OK” button to close the dialogue box; 

- Answer “Yes” to the question “Do you really want to calibrate the images in the group?” to activate the calibration procedure - The calibrated images are saved in the same folder as the image file list;

- Close EDPIV.

 

(a) Particle image recording before calibration

 

(b) Particle image recording after calibration

 

 

PART 3 - EVALUATION WITH CALIBRATED IMAGE

Step 1: Generate image file list

- Execute file “Edpiv.exe” - The start window is shown on the screen;

- Select menu “Edit \ File list” - Dialogue box “Creating file list” appears;

- Press “Input files” button - Dialogue box “Data file list” appears;

- Browse hard drives to find folder that contains the calibrated images;

- Arbitrarily select one of the image files, and then press “Open” button;

- Press “Output file” button - Dialogue box “Data file list” appears again;

- Browse the hard drives to find a desired destination folder;

- Type a name for the file list in the edit box indicated by “File name”, and then click “Save” button;

- Set “Recording type” to 2;

- Press button “Create” to generate the image file list;

- Close the dialogue box to return to the start window.

Step 2: Open PIV image group

- Click menu “File \ Image group” - Dialogue box “Recording group” appears;

- Browse the file system to find the image file list created in step 1;

- Click “Open” - The first image of the first pair is shown in the picture frame.

Step 3: Determine imaging scale and time interval 

- Click menu “Edit / Scale & time” in the start window to open dialogue box “Imaging scale / time interval”;

- Select radio button mm;

- Determine imaging scale by
Inputting
100 in edit box “Reading on ruler”
Inputting
1024 in edit box “Corresponding pixels”;

- Set up time interval as 20000 microseconds (mu-s);

- Press “OK” button to return to start window.

Step 4: Setup evaluation parameters

- Click menu “Edit / Evaluation settings” in the start window to open the “Evaluation settings” window;

- Setup parameters as follows
Method & algorithm:
PIV
Ellipse window: Selected
Recording type:
Recording group: ensemble evaluation
Exposure type:
Single
Flow type:
One phase
Initial window shift:
(X,Y), X=0, Y=0
Interrogation grid: 16x16
Error limits:
Dx=2, Dy=2
Iteration number:
0 (Initial), 6 (Final) 
Window width :
32 (Initial), 32 (Final)
Window height :
32 (Initial), 32 (Final)
Search radius:
12

- Close “Evaluation settings” window.

Step 5: Evaluate the PIV recording group

- Press button “Evaluation” in the start window - “Evaluation” window is opened, and a regular interrogation grid is ready;

- Click menu “Start” in “Evaluation” window;

- Answer “Yes” to question “Do you want to start an evaluation?”

- Wait until the evaluation is completed;

- Press “OK” to close the dialogue box that notices the end of the evaluation;

Step 6: Save evaluation result

- Click menu “File \ Save data” - Dialogue box “Save evaluation results” appears;

- Find a desired folder, type in a file name in the dialogue box;

- Press button “Save” to complete the saving procedure.

Step 7: Plot vector map

- Close EDPIV;

- Use TECPLOT to make plots.

 

 

 

PART 4 - EVALUATION WITH GRID/VECTOR CALIBRATION

Step 1: Open PIV image group

- Execute file “Edpiv.exe” - The start window is shown on the screen;

- Click menu “File \ Image group” - Dialogue box “Recording group” appears;

- Browse the file system to find the image file list created in Part 2, Step 1;

- Click “Open” - The first image of the first pair is shown in the picture frame.

Step 2: Import calibration function

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Click mouse at calibration function check button “N” - Dialogue box “Calibration function” appears;

- Select radio button “Import” and then press button “OK” - Dialogue box “Import image calibration data” appears;

- Browse hard file system to find the file created in Part 1, Step 4, and press “Open” button;

- Close dialogue box “Stereo/distorted PIV recording”;

Step 3: Determine image view area and time interval

- Click menu “Edit / Scale & time” in the start window to open dialogue box “Imaging scale / time interval”;

- Set up view area as X0=0, Y0=0, X1=100, Y1=100;

- Setup time interval as 20000 microseconds (mu-s);

- Press “OK” button to return to start window.

Step 4: Setup evaluation parameters

- Click menu “Edit / Evaluation settings” in the start window to open the “Evaluation settings” window;

- Setup parameters as follows
Method & algorithm:
PIV
Ellipse window: Selected
Recording type:
Recording group: ensemble evaluation
Exposure type:
Single
Flow type:
One phase
Initial window shift:
(X,Y), X=0, Y=0
Distorted/stereo PIV calibration:
Grid/vector, Normal
Interrogation grid:
16x16
Error limits:
Dx=2, Dy=2
Iteration number:
0 (Initial), 6 (Final) 
Window width :
32 (Initial), 32 (Final)
Window height :
32 (Initial), 32 (Final)
Search radius:
12

- Close “Evaluation settings” window.

Step 5: Evaluate the PIV recording group

- Press button “Evaluation” in the start window - “Evaluation” window is opened, and a regular interrogation grid is ready;

- Click menu “Start” in “Evaluation” window;

- Answer “Yes” to question “Do you want to start an evaluation?”

- Wait about 6 minutes (P-4 2.5GHz) until the evaluation is completed;

- Press “OK” to close the dialogue box that notices the end of the evaluation.

Step 6: Save evaluation result

- Click menu “File \ Save data” - Dialogue box “Save evaluation results” appears;

- Find a desired folder, type in a file name in the dialogue box;

- Press button “Save” to complete the saving procedure.

Step 7: Plot vector map

- Close EDPIV;

- Use TECPLOT to make plots.